Hairspring collet



Nov. 14, 1950 F. MAR-f1 mmsmnc com Filed March 28, 1946 Patented Nov. 14, 1950 UNITED STATES PATENT OFFICE HAIRSPRING COLLET Fritz Marti, La Chaux de Fonds, Switzerland Application March 28, 1946, Serial No. 657,874 In Switzerland May 5, 1945 2 Claims. 1

The object of the present invention is a collet in two pieces for the instantaneous attachment of a balance wheel hair spring. This collet is characterized by two pieces intended to be thrust on the stafi of the balance wheel, the first one presenting a passage for the end of the hair spring, the second one fitting in the first one and presenting on the one hand a clamping element of the balance wheel staif, and on the other hand a clamping element of the hair spring in the first piece, the whole enabling attaching and removing quickly the balance wheel hair springs.

The attached drawing shows by way of example an embodiment of the invention.

Fig. 1 is an axial section and Fig. 2 a plan view thereof.

Fig. 3 is a section of a detail along line III-III of Fig. 2.

Figs. 4 and 5 show the collet in two diiferent positions, one before and the other after the attachment of the hair spring.

In the embodiment shown, the collet comprises a ring I made hollow in one side, so as to form a small cylindrical box. This ring presents in its hollow edge two lateral notches 2 intended to let pass the end of the hair spring 3 to be attached on the collet.

A resilient U-shaped member 4 is arranged to rotate freely in the ring I. This member is intended to be thrust on the balance wheel stall at the same time as the ring, and to pinch this staff between its two branches. On its periphery, the U-shaped resilient member presents a circular recess 5 intended to let pass the hair spring when the latter is being attached. The mode of utilization of this collet is as follows:

The inner end of the hair spring is passed through the notches of the ring, the U-shaped piece being in the position shown in Fig. 4. For attaching the hair spring on the collet, it is then suflicient to rotate the U-shaped member by a quarter of a turn, by means of a suitable tool.

The hair spring can first be mounted on the ring, in the manner described, and then the ring can be thrust on the balance wheel staff. One can also first put the ring on the balance wheel staff and then pass the hair through the notches of the ring and tighten it by turning the U-shaped member.

The removal is effected by carrying out the reverse operations.

The advantage of this collet is to enable to mount or remove quickly the balance wheel hair springs.

What I claim is: I

1. In combination with a balance-wheel staff, a hair spring, a collet having the form of a sleeve provided with a side wall and adapted to be thrust on the balance-wheel staff, and having two lateral notches in said side wall to let pass the inner end of the hair spring, a U-shaped member com prising two branches connected by a transverse bar rotatably mounted within said sleeve, said member being adapted to clamp upon rotation thereof the hair spring between its transverse bar and the inner wall of said sleeve.

2. In combinationwith a balance-wheel staff, a hair spring, a collet having the form of a sleeve provided with a side wall and adapted to be thrust on the balance-wheel staff, and having two lateral notches in said side wall to let pass the inner end of the hair spring, a resilient U-shaped member comprising two branches connected by a transverse bar rotatably mounted within said sleeve and pinching the balance staff between its branches, said member being adapted to clamp upon rotation thereof the hair spring between its transverse bar and the inner wall of said sleeve.

FRITZ MARTI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,283,705 Ecaubert Nov. 5, 1918 2,419,103 Whitehead Apr. 15, 1947 

